The adsorption and decomposition of diethylgermane, GeH2(C2H5)2 (or GeH2Et2), on the Si(100)-(2 x 1) surface is investigated with the intent of elucidating the surface processes leading to the deposition of epitaxial Ge thin films from gaseous Ge-containing sources. Low GeH2Et2 exposures to Si(100) at 110 K result in dissociative adsorption of the molecule with both ethyl groups transferring to the silicon surface. Heating of the sample to higher temperatures results in the decomposition of the adsorbed ethyl groups. GeH2 is the other adsorption product which also decomposes at higher temperatures to atomic Ge. The final reaction products are H-2, C2H4, and atomic Ge. The ethylene produced is consistent with a beta-hydride elimination reaction.